The main objective of this prospective longitudinal study was to investigate bidirectional associations between adolescent cannabis use (CU) and neurocognitive performance in a community sample of 294 young men from ages 13 to 20 years. The results showed that in early adolescence, and prior to initiation to CU, poor short-term and working memory, but high verbal IQ, were associated with earlier age of onset of CU. In turn, age of CU onset and CU frequency across adolescence were associated with (a) specific neurocognitive decline in verbal IQ and executive function tasks tapping trial and error learning and reward processing by early adulthood and (b) lower rates of high-school graduation. The association between CU onset and change in neurocognitive function, however, was found to be accounted for by CU frequency. Whereas the link between CU frequency across adolescence and change in verbal IQ was explained (mediated) by high school graduation, the link between CU frequency and tasks tapping trial and error learning were independent from high school graduation, concurrent cannabis and other substance use, adolescent alcohol use, and externalizing behaviors. Findings support prevention efforts aimed at delaying onset and reducing frequency of CU.

This research was made possible by a fellowship (to N.C.-R.) from the Ministère de l’Éducation, du Loisir et du Sport du Québec (No. 149169) and the Fonds de Recherche en Santé du Québec (No. 22530); and grants from the Canadian Institutes of Health Research (MOP-97910), the Social Science and Humanities Research Council of Canada (412-2000-1003), the National Health Research and Development Program, the Fonds Québécois de Recherche sur la Société et la Culture (2002-RS-79238 and 2009-RG-124779), the Fonds Québécois de Recherche en Santé, the American National Science Foundation (SES-9911370), and the National Consortium on Violence Research (supported under Grant SBR-9513040 from the National Science Foundation). These funding agencies had no role in the study design, collection, analysis, or interpretation of the data; writing the manuscript; or the decision to submit the paper for publication. The authors thank the boys, their families, and teachers for their long-term commitment to this project.

Footnotes

This research was made possible by a fellowship (to N.C.-R.) from the Ministère de l’Éducation, du Loisir et du Sport du Québec (No. 149169) and the Fonds de Recherche en Santé du Québec (No. 22530); and grants from the Canadian Institutes of Health Research (MOP-97910), the Social Science and Humanities Research Council of Canada (412-2000-1003), the National Health Research and Development Program, the Fonds Québécois de Recherche sur la Société et la Culture (2002-RS-79238 and 2009-RG-124779), the Fonds Québécois de Recherche en Santé, the American National Science Foundation (SES-9911370), and the National Consortium on Violence Research (supported under Grant SBR-9513040 from the National Science Foundation). These funding agencies had no role in the study design, collection, analysis, or interpretation of the data; writing the manuscript; or the decision to submit the paper for publication. The authors thank the boys, their families, and teachers for their long-term commitment to this project.